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>> Monday, November 9, 2009

Boeing B777 - GE90-115B Engines - Low Pressure Turbine Borescope

Background/Reason:
On condition requirement of an engine requires periodical inspection of internal condition of certain critical rotating parts. The exact rate of change of these hardware conditions from the initial condition can be regularly monitored and on a planned basis, the engines can be removed, when these critical parts have reached its maximum life for repair/refurbishment/overhaul/replacement.

Note: The Circuit breakers listed below are for both engines. Tag & install safety tags depending on engine to be inspected.

2. Retract the leading edge slats as per AMM 27-81-00-860-805.
3. Deactivate the leading edge slats as per AMM 27-81-00-040-801.
4. Deactivate the Thrust Reverser for ground maintenance as per AMM 78-31-00-040-806-H00.
5. Open the fan cowl as per AMM 71-11-04-010-814-H00.
6. Open the thrust reverser cowl as per AMM 78-31-00-010-816-H00.
7. Refer to Fig 1 & Fig 2 and remove the borescope plugs R & S.
8. Insert Borescope Probe through port R or port S as per AMM.
9. Refer to figs 3 to 6 & rotate the Fan Clockwise as per AMM 72-00-00-290-807-H01 & inspect the LPT blades leading edges and trailing edges and complete the Table 1.
10. Remove borescope probe from Ports after completing the borescope inspection as per AMM.
11. Apply Antiseize compound on the borescope plugs R & S.
12. Install the borescope plugs R & S as per AMM 72-00-00-420-001-H01. Note: Tighten the plugs to 110.0-140.0 pound-inches (12.4-15.8 Newton-meters)
13. Carry out duplicate inspection of installation of the borescope plugs R & S as per AMM 72-00-00-420-001-H01.
14. Close the Thrust Reverser as per AMM Task 78-31-00-410-816-H00.
15. Close the Fan Cowl as per AMM Task 71-11-04-410-814-H00.
16. Activate the Thrust Reverser as per AMM 78-31-00-440-805-H00.
17. Activate the leading edge slat as per AMM 27-81-00-440-801.
18. Remove the safety tags and close these circuit breakers: